Switchable light-collimating layer with reflector

Abstract

A light-collimating film including elongated chambers of bistable electrophoretic fluids. The light-collimating films are suitable to control the amount and/or direction of light incident to a transmissive substrate. Such films may be integrated into devices, such as LCD displays, to provide a zone of privacy for a user viewing the LCD display. Because the light-collimating film is switchable, it allows a user to alter the collimation of the emitted light on demand. Because the films are bistable, they do not require additional power after they have been switched to a display state.

The invention claimed is: 
     
       1. A switchable light-collimating film comprising:
 a first light-transmissive electrode layer; 
 a collimating layer having a thickness of at least 20 μm, and comprising a plurality of elongated chambers with a portion of collimating layer between elongated chambers, each elongated chamber having an opening; 
 a bistable electrophoretic fluid comprising pigment particles disposed in each elongated chamber; 
 a sealing layer including light-reflective materials that seals the bistable electrophoretic fluid within at least one of the plurality of elongated chambers by spanning the opening of the elongated chamber; and 
 a second light-transmissive electrode layer, wherein the first and second light transmissive layers are disposed on either side of the collimating layer; 
 wherein the sealing layer provides a light-reflective surface aligned with the opening of each elongated chamber, and wherein the light-reflective surface does not substantially overlap with the portion of the collimating layer between elongated chambers. 
 
     
     
       2. The switchable light-collimating film of  claim 1 , wherein the collimating layer has a thickness of less than 500 μm. 
     
     
       3. The switchable light-collimating film of  claim 1 , wherein a height of the elongated chambers is equal to or less than the thickness of the collimating layer, a width of the elongated chambers is between 5 μm and 150 μm, and a length of the chambers is between 200 μm and 5 mm. 
     
     
       4. The switchable light-collimating film of  claim 1 , wherein the collimating layer comprises a polymer including acrylate monomers, urethane monomers, styrene monomers, epoxide monomers, silane monomers, thio-ene monomers, thio-yne monomers, or vinyl ether monomers. 
     
     
       5. The switchable light-collimating film of  claim 1 , wherein the light-reflective surface comprises a metal or a light-reflective metal oxide. 
     
     
       6. The switchable light-collimating film of  claim 1 , wherein the first or second light-transmissive electrode layer comprises indium-tin-oxide. 
     
     
       7. The switchable light-collimating film of  claim 1 , wherein the bistable electrophoretic fluid comprises polymer-functionalized pigment particles and free polymer in a non-polar solvent. 
     
     
       8. The switchable light-collimating film of  claim 7 , wherein the pigment is functionalized with a polyacrylate, polystyrene, polynaphthalene, or polydimethylsiloxane. 
     
     
       9. The switchable light-collimating film of  claim 7 , wherein the free polymer comprises polyisobutylene or copolymers including ethylene, propylene, or styrene monomers. 
     
     
       10. The switchable light-collimating film of  claim 1 , wherein the sealing layer comprises cellulose, gelatin, a polyacrylate, a polyvinyl alcohol, a polyethylene, a poly(vinyl) acetate, a poly(vinyl) pyrrolidone, a polyurethane, or a copolymer of any of the aforementioned polymers. 
     
     
       11. The switchable light-collimating film of  claim 1 , wherein the light-reflective surface contacts the bistable electrophoretic fluid. 
     
     
       12. The switchable light-collimating film of  claim 1 , further comprising an optically-clear adhesive layer. 
     
     
       13. The switchable light-collimating film of  claim 12 , further comprising a release layer adjacent to the optically-clear adhesive layer. 
     
     
       14. A display comprising a switchable light-collimating film of  claim 1 . 
     
     
       15. A display comprising:
 a light source; 
 a switchable light-collimating film comprising: 
 a first light-transmissive electrode layer, 
 a collimating layer having a thickness of at least 20 μm, and comprising a plurality of elongated chambers with a portion of collimating layer between elongated chambers, each elongated chamber having an opening, 
 a bistable electrophoretic fluid comprising pigment particles disposed in each elongated chamber, 
 a sealing layer including light-reflective materials that seals the bistable electrophoretic fluid within an elongated chamber by spanning the opening, and 
 a second light-transmissive electrode layer, wherein the first and second light, transmissive layers are disposed on either side of the collimating layer, 
 wherein the sealing layer provides a light-reflective surface aligned with the opening of each elongated chamber, and wherein the light-reflective surface does not substantially overlap with the portion of the collimating layer between elongated chambers; 
 an active matrix of thin film transistors; 
 a liquid crystal layer; and 
 a color filter array. 
 
     
     
       16. The display of  claim 15 , further comprising a voltage source and a controller to provide a voltage impulse between the first and second light-transmissive electrode layers. 
     
     
       17. The display of  claim 15 , further comprising a prism film disposed between the light source and the switchable light-collimating film. 
     
     
       18. The display of  claim 15 , further comprising a diffusion layer between the prism film and the light source. 
     
     
       19. The display of  claim 15 , further comprising a touch screen layer. 
     
     
       20. The display of  claim 15 , wherein the light-reflective surface is disposed between the light source and the active matrix of thin film transistors. 
     
     
       21. The switchable light-collimating film of  claim 1 , wherein the light-reflective materials comprise metal flakes or titanium dioxide. 
     
     
       22. The display of  claim 15 , wherein the light-reflective materials comprise metal flakes or titanium dioxide.